Commercial condoms have been manufactured from natural rubber (NR) latex for over sixty years. NR latex is an excellent material for the latex dipping process customarily employed for producing such articles as condoms, medical gloves, and the like, since it is stable and can readily be compounded with aqueous dispersions of curatives, e.g. sulphur, zinc oxide, preservatives etc. Also the actual dipping process is simple since a congruent film is formed on the shape former when it is dipped into the latex. Further, on the application of heat, water is rapidly evaporated and a natural rubber film of uniform thickness and integrity is formed.
It is general practice to dip the former, with the dried rubber film on it, into the latex a second time in order to minimize the presence of holes in the condom. After sulphur vulcanization by heating at 100.degree. C. for about one hour, NR condoms exhibit high tensile strength and extensibility and good tear resistance. However since natural rubber is an unsaturated hydrocarbon elastomer, it has poor resistance to degradation by heat, light, oxygen, ozone, and bacteria. Also traces of metals, such as copper, accelerate the degradation.
Natural rubber is also readily swollen, weakened, and degraded by contact with chemical fluids, in particular by hydrocarbon oils and solvents. It is well known that NR condoms are seriously weakened when lubricated by mineral oil, petroleum jelly, and vegetable oils, as well as by some ingredients in feminine hygiene products and therapeutic creams. Occasionally, after contact with such materials, condoms will fail in use by tearing or disintegrating.
Laboratory examination gloves and surgeons' gloves are usually made from natural rubber latex. Although such gloves are sufficiently strong and durable for handling medical devices, physical contact etc., they are also readily weakened by contact with laboratory chemicals, hygiene products, dental compounds, mortuary fluids, etc. Thus, there is a significant commercial and safety incentive to produce gloves, condoms, and other elastomeric film products from a synthetic latex which would give a superior resistance to chemicals, lubricants, etc. Also, for the majority of users it is necessary to lubricate condoms. Since there is no natural rubber compatible lubricant available to the user directly, most condoms are prelubricated at the factory using specialty silicone oils, which are unavailable to the general public. By the nature of these low viscosity oils, the method of application and packaging, the condoms are themselves completely covered on the inner and outer side by the lubricant. The lubrication on the inside of the condom facilitates unwanted slippage and strain that could increase the incidence of strain-induced failure or loss of the condom during normal use.
A chemical resistant condom would allow implementation of the single sided lubrication concept using selected household lubricants, such as petroleum jelly, baby oil, etc. This could significantly reduce the condom failure rate by decreasing the actual strain experienced by a single sided lubricated condom. The decreased strain would result from the increased adhesion of the condom to the skin resulting from elimination of lubrication on the inside of the condom, while maintaining the outer lubrication layer that appears to be needed in the clinical environment.
More recently, there has been clarification of the possible serious allergic reactions of some persons caused by contact with natural rubber latex products. Protein residues in the latex products are the causative factors of these allergic reactions. Such reactions can lead to contact urticaria or systemic anaphylaxis. In other terms, persons with such allergies can experience itching, rashes, wheezing, or more severe symptoms when they use NR latex condoms or gloves. For this reason, and for other technical and economic factors, the manufacturing industry would like to develop the use of non-allergenic synthetic latex materials such as the materials disclosed in this application.
The present invention provides an elastomeric film product such as a condom of enhanced chemical resistance. Because of this improved chemical resistance, it is possible to employ lubrication systems that will reliably coat only the outside of the condom. The lubricant is added to the outside of the condom via a solvent and the coating is dried before rolling. This prevents the transfer of the lubrication system from the outside to the inside. As a number of these lubricants must be applied from non-aqueous solvent systems, only a chemically resistant condom can be employed with such lubricants.
Also, users will be able to employ nontoxic petroleum based lubricants found in their home to satisfy any additional needs for lubrication. Further, the condom provided by this invention will allow women to continue medicament-based vaginal therapy with a significantly decreased risk of condom failure that could be caused by excipient interaction with the condom.